In a pivotally mounted angle joint, which is known from German Auslegeshrift (Published Patent Application) No. 25 12 253, the locking element is in the form of a flexible web integral with the ball socket which is made of thermoplastic material. When the ball of the ball pivot is pushed into the socket recess, the said web is deflected perpendicularly to the direction of insertion of the ball and is moved flexibly behind the recess after the ball is pushed fully into the said recess. During movement to remove the ball in the opposite direction to the directon of insertion, the said web would be flexibly deflected in the same manner. In order to prevent this, a filling piece is driven into a recess formed on the turned away side of the web after the ball snap-engages flexibly in the recess, the said flexible web being fixed, in its locking position, by means of the filling piece. The principal disadvantages of this form of ball socket is, just as with numerous other ball sockets which must be sealed by a separate part, the work involved in driving in the filling piece and the fact that the filling piece can be lost. During fitting, the fitter may completely forget the driving-in operation, since the filling piece is very small, thereby making it possible for the ball pivot to be detached from the ball socket, which should not occur under any circumstances for reasons of safety. Finally manufacture of this ball socket is not an easy operation since the flexible web, which forms the locking element, must be deformed when the core forming the recess is removed. Finally, it is also very difficult for the ball pivot to be deliberately detached from the ball socket since the filling piece must again be driven out of the ball socket.
It appears conceivable to reduce the fitting problems, described above, by providing the ball socket with a semispherical recess having an adjacent cylindrical face leading to the opening. Furthermore, a leaf spring should be provided on the outer face of the ball socket, which encompasses the ball socket and which, with ends bent obliquely inwards, engages in the recess by means of corresponding skewed slots or channels. When the ball of the ball pivot is pushed into this recess, the ends of the leaf spring, while being braced, would be pushed out through the slots and, while partially gripping the rear of the ball, would cause the latter to spring back into the recess after the said ball is fully pushed into the recess. Such an embodiment would be extremely disadvantageous since leaf springs cannnot be produced with such precision that a firm and therefore rattle-free fit of the ball in the ball socket would be ensured. Moreover, flaws in the temper of the leaf spring could very easily lead to their breakage. Finally, the free ends of the leaf springs, while being pushed out through the oblique slots or channels, could become wedged therein, which would jeopardize at least the operation of re-engagement.